Glacier Hydrology References Revision

Stuart et al., 2003

• Ground-penetrating radar profiles were used to collect data on an englacial channel system for cold-glacier austere Brøggerbreen, Svalbard

• The size of conduits varied from a large semicircular channel at 5m wide to a vertically elongated 2.5m channel close to the outlet as well as variations in the depth of water in the channel from 14 to 90% of channel height 

• Results of dye-tracing experiments combined with the low channel gradient of less than 2 degrees suggests that there is significant ponding along the channel; radar reflections were useful in determining the depth, dimensions and water content of these englacial watercourses

• This channel geometry was probably formed during a period of increased crevassing from the Little Ice Age, these channel dimensions were sourced from direct descent into the moulin to verify these interpretations through glacio-speleology

Samimi & Marshall, 2017

• Meltwater refreezing and storage in the superglacial snowpack can reduce and delay meltwater runoff from glaciers, but the effect of these processes are often uncertain for temperate alpine glaciers

• The temperature and meltwater content in the upper 50cm of the supraglacial snowpack of Haig Glacier was measured using thermistorics and Time Domain Reflectometry (TDR) probes and supplemented by automatic weather station data 

• These methods found strong diurnal cycles in snow water content through the summer melt season with subsurface refreezing only significant in May, after this overnight freezing was restricted to only a thin surface layer of the snowpack; here diurnal variation in supraglacial hydrology were revealed showing high levels of water stored in the daytime contrasting with minimum levels overnight 

• Overnight decreases in water content after May were associated with meltwater percolation and drainage; overall there was a negligible meltwater retention in the snow on a daily basis

Hock & Hooke, 1993

• During the 1989 melt season, 10 tracer experiments were conducted to investigate the seasonal, diurnal and spatial variations in the englacial drainage system of Storglaciarien, Sweden where dye was injected into moulins and its concentration and discharge monitored at the glacier terminus 

• Transit velocities ranged from 0.07 to 0.29 m/s, implying that drainage was initially taking place through a well-defined conduit system as part of a multi-branched aborescent network of wide, low passages; this dispersivity declined during the early part of the meltseason to reflect structural changes in conduits including a decrease in braiding and increase in size before the final configuration was reached in early August

• The conduits were found to be full of water during periods of higher daily discharge with water pressure exceeding atmospheric pressure

• Overall, variation in tracer return curves and dispersivity on a diurnal time scale reflect changes in the degree of braiding as lower divides are drowned between channels and discharge increases

Fountain et al., 2005

• The prevailing hypothesis explains that water flow through the body of a glacier takes place in a network of tubular conduits; however, video images from 48 boreholes drilled into Storglaciӓren, Sweden, shows that the hydrological system  is instead dominated by fractures converting water at slow speeds at all depths

• Fractures provide the main pathways for surface water to reach deep within the glacier whereas conduits only form in special circumstances

• These fractures are useful in explaining the evolution of the englacial water flow system, seasonal regeneration and in understanding the collapse of ice shelves and hydraulic connection between the surface and bed of an ice sheet

• Findings from this study expose claims to universality within englacial theory and instead provide evidence for spatial variation between and within glaciers

Benn & Evans, 2010

• The production, storage and transport of water has a profound influence on glacier behaviour as water contributes to glacial erosion, debris transport and deposition as a direct agent; water released from glaciers also present benefits and hazards for human populations through cultivating valleys for agriculture, hydroelectricity and flooding

• The contrasting permeabilities of snow and ice mean that supraglacial drainage systems on snow-covered surfaces and bare ice are very different; on snow the water readily percolates through pore spaces until it reaches the freezing point, this kind of drainage becomes more efficient over time as rills and surface channels form; for ice surfaces the meltwater cannot percolate as the ice is impermeable so much run off the surface in sheet flows or channels 

• The englacial drainage system conveys surface meltwater to the bed of glaciers, for many years models of englacial drainage were based on the theoretical model developed by Shreve in 1972 but this did not provide a realistic picture of actual drainage as they show no tendency to follow theoretical potential gradients and do not behave as predicted

• Insights into the character of englacial drainage systems have been developed through video imaging of boreholes, ice cores, glacio-spelology and surface geophysical surveys that reveal important insights to challenge assumptions of conduits being semicircular without variation, that these dominate water flow and into their seasonal, diurnal and geographical variation

• Subglacial channels may be incised into the ice or cut into the glacier bed, they develop through creep closure leading to the development of branches drainage systems that can fluctuate in response to diurnal and weather related variations in melting; these channels cannot always be assumed to be semicircular but instead have complex forms, travel in many directions and are subject to strong seasonal variation

Miles et al., 2020

• The hydrological characteristics of debris-covered glaciers are known to be fundamentally different from those of clean-ice glaciers, this influences the timing and magnitude of meltwater discharge to impact communities who rely on this for sanitation, irrigation and hydropower 

• The rugged surface of debris-covered glaciers means supraglacial systems are likely to involve channels and ponds as well as unknown pathways; englacial conduits are frequently abandoned and reactivated as water supply changes, new lines of permeability are exploited and drainage captured as well as being subject to the seasonal influence of monsoons that reorganise these systems rapidly

• This study used dye tests on debris-covered Khumbu Glacier in Nepal to infer the existence of a channelised subglacial drainage system that discharge large volumes of heavily debris-laden water during the melt season

• It was inferred that the subglacial system increased in efficiency and interconnection throughout the melt season; this channelised system was revealed but there was no evidence found for the evolution of the system from, or returning to, cavities showing greater spatial variability in subglacial drainage systems around the world

Church et al., 2020

• Between 2012 and 2019 repeated GPR surveys were carried out over an active englacial conduit network within the ablation area of temperate Rhonegletscher in Switzerland, this showed that during the summer melt seasons there are active, water-filled, sediment transporting englacial conduit networks 

• The surveys provided evidence that the conduits were up to 20m wide and formed by hydraulic fracturing 

• During the winter, the englacial conduit no longer transports water and became physically closed or very thin to produce, following the melt season this reactivated in the exact same position

• This highlights the importance of observations in testing englacial hydrology theory to allow it to capture greater spatial and temporal variability

Campbell et al., 2006

• Dye tracing was conducted in the 2004 melt season at Haut Glacier d’Arolla, Switzerland, to better understand the role of the supraglacial snowpack in mediating the delivery of meltwater produced by the snowpack surface to the rest of the glacier with implications for proglacial forms and subglacial water pressure

• Observations show the complexity of flow patterns to yield average flow rates for percolation through the snowpack of between 0.13 and 0.49 m/h with an increase in percolation rates over the course of the melt season in the efficiency of which the snowpack transmits water 

• The reason for an increase in percolation rates over the course of the melt season is attributed from the progression of the snowpack from an initial cold, impermeable surface to a warmer, better connected layer facilitating more rapid percolation by the end of the melt season and proving that the dampening effect of the snowpack varies seasonally  

• Snow permeability in this study was found to be significantly lower than previous studies, showing a need for improved research on snowpack hydrology

Willis et al., 2012

• Digital elevation models of the surface and bed of a glacier can be used to calculate the subglacial hydraulic potential and infer drainage system structures, a distributed degree day model is also used to calculate the spatial distribution of melt on the glacial surface to impact water flux beneath the glacier

• Comparisons of 78 dye tracing tests over 33 injection sites as well as measures of water discharge suggest that the temporally and spatially averaged steady state water pressure beneath the glacier were around 70% over ice burden meaning k equalled 0.7 in the hydraulic potential equation for subglacial hydrology

• This shows that the main drainage network of the eastern half of the glacier consists of hydraulically efficient systems of broad, low channels and the smaller drainage system on the west consists of hydraulically ineffective distributed systems with very broad low channels showing how the subglacial drainage system can vary within an individual glacier

Fountain & Walder, 1998

• It is important to understand water movement through glaciers to understand glacier dynamics, glacier-induced floods and predict runoff

• Firn can influence the supraglacial drainage system as when it is porous and permeable the flux of water to the glacier interior varies slowly due to the firn temporarily storing water and smoothing out variations in supply through the dampening effect; however, in the firn-free ablation zone the flux of water depends directly on the rate of surface melt or precipitation

• In the englacial drainage system the water moves from the surface to the bed through a network of steep conduits that deliver water to the bed, in the accumulation zone these are steady state features that convey water delivered via firn so are usually full of water and pressurized; in the ablation area they are only pressurised near times of daily flow or during storms 

• The subglacial drainage system can be made up of many distinct elements from a branching network of channels to a more extensive network of nonarborescent channels converting water slowly and poorly connected; the arborescent channel largely collapses during the winter but reforms in the spring as the bed disabilities cavities in the non-arborescent network 

• The volume of water stored by glaciers varies diurnally and seasonally with daily fluctuations of up to 20-30 mm; most water storage is likely to occur englacially and if this is abruptly released it can lead to catastrophic flooding

• This shows that there are great variations in the hydrology of an individual glacier between the accumulation and ablation zone

Cuffey & Paterson, 2010

• The hydrological system of glaciers can be broken down into three main categories; the supraglacial, englacial and subglacial systems that examine the movement of water on the surface of the ice, within the ice, and at the glacier bed

• Within each of these categories, there is a plethora of theories on how runoff, transportation and drainage systems are characterised; these often first come from widely accelerated theoretical analyses of hydrological processes that are then tested, critiqued and improved through the observations and the application of empirical data

• Observations are collected from the field in a number of water including drilling boreholes into ice, ice core examination, dye testing and glacio-speleology that can be combined with remote sensing methods including ground-penetrating radar (GPR) analyses

• There remains a need to continue to develop observation techniques and combine them in innovative ways to fill gaps in knowledge on glacier systems

UNESCO World Water Assessment Programme, 2025

• In March of 2025, the UN World Water Development Report found that the 2 billion people worldwide who depend on glacier meltwater for sanitation, irrigation and water security were set to face ‘severe’ consequences to their livelihoods as glaciers continue to melt as a result of anthropogenic climate change

• This impact is exacerbated as glacier melt has a profound effect on glacier hydrology by changing the volumes and timings of runoff leading to glacier behaviours changing and impacts to humans being altered

• Glacier hydrology theory is key to predicting the extent of these changes and ensuring appropriate measures are taken to reduce risks to populations that rely on glaciers to support their lifestyles

Milner et al., 2017

• Glaciers cover around 10% of Earth’s land surface but are shrinking rapidly across most parts of the world leading to cascading impacts to downstream systems as a result of changes in river hydrology and morphology bought on my glacier shrinkage 

• Understandings of glacier mass loss have improved significantly in the past decade due to advances in remove sensing and processing direct measurements, there should be increased attention to how climate driven changes in glacier volume alter the timing, magnitude and frequency of downstream discharge, sediment transport and nutrients with far reaching impacts to ecosystems, societies and human activities 

• Glacier runoff typically peaks during the summer when runoff from other sources is lower to act as a buffer against dry season stream discharge from precipitation variability; however, as glacier cover declines this annual runoff will be reduced due to a decline in glacier volume after an initial earlier peak caused by the earlier disappearance of reflective snow cover to lower surface albedo 

• These glacier runoff changes replace predictable hydrographs with more variable hydrological regimes fed mainly by unpredictable rainfall and snowmelt runoff regimes; this will lead to an increase in summer water temperature due to a decline in contribution of cold water from glacier melt, increase in air temperature and reduced heat capacity as well as a decrease in sediment load as glacial erosion reduces

• There will be a decrease in glacially supplied dissolved atmospheric organic carbon, nitrogen, phosphorus and other organic elements which may lead to a decrease in biodiversity as streams and rivers physical and chemical conditions change, this means organisms unable to adapt become extinct such as salmon and trout as a result of rising temperature; this also has a knock-on effect on the food web

• Seasonal predictable melt facilitates a range of important socioeconomic ecosystem services, disruptions to these are particularly important in semiarid and arid regions where water source contributions are limited; this can impact irrigation, hydropower, fisheries, water quality and cultural services